Electromechanical switching system



June 24, 1930. F. ALDENDORFF ELECTROMECHANICAL SWITCHING SYSTEM 4 Sheets-Sheet 2 Filed Sept. 50, 1927 Fig. 2. I

Jnven tor a a T000000 P000000 o o 0 9 0 o ATTaRNEq Patented June 24, 1930 it a 133,281

FFEQE' FRITZ ALDENDORFF, OF BER-LIN, GERIEANY; CHARLOTTO ALDENDGRFF, WIDOVI AND SOLE I-IEIR 0F SAID FRITZ ALDENDORFF, DECEASED, ASSIGNOR TO WESTERN ELEG- TBIIC COMPANY, INCORPORATED, OF NE'lV YORK, N. Y., A CORPGRATION OI NEW YORK ELECTROMECI-IANICAL SFI'ITCHING SYSTEM Application filed September 3-0, 1927, Serial No. 223,169, and in Germany October 6, 1926.

finder arrangements for line-finders with brushes, each of which moves always in one plane only. According to the invention the line-finders themselves place their starting magnets or starting relays into communica tion with the starting line or lines aifected by the calling line or lines, whereby the provision of one or more trunk finders can be dispensed with.

Of a group of line-finders, one free linefinder goes into a position of readinessiin which it receives the next call arriving in the group. As soon as a line-finder leaves the position of readiness another free linefinder passes over into the position of readiness. Of the free line-finders one goes into the position of readiness and the others into waiting positions from which they pass over one after the other into the position of readiness. In the event of, on the occurrence of a call, no line-finder being in the waiting position immediately before the position of readiness, a particular arrangement causes the movement of a free line-finder into the waiting position and thence into the position of readiness. If on the arrival of a call no free line-finder is in one of the waiting positions next before the position of readiness, then all the free line-finders are simultaneously caused to move forward into the waiting positions and one of them is brought into the position of readiness and from this to the calling line.

A further feature of the invention consists in the use of feeling relays, which on the arrival of a call feel the waiting contacts of a groupof line-finders one after another until, through one of them, a starting current flows for a free line-finder located in the waiting position. If on the arrival of a call no current flows through the feeling relay and through a waiting contact then all the free line-finders are started by a group starting relay. The different free line-finders set themselves on to waiting positions, each of which may be located at the beginning of a diiferent sub-group of bank contacts. In addition to a starting line controlled by the calling relays of the calling lines and controlling the starting relays of the line-finders in readiness, a moving up line controlled by the relays of the linefinders is provided which controls the linefinders which are in thewaiting position. Each line-finder of a group closes a current lead to its starting relay in a position of its brushes, which differs from the position in which each of the other line-finders closes a corresponding current lead, so that the brushes of the line-finders are all located in front of different bank contact subgroups, when the current leads mentioned are closed. The current lead to the starting relay can be effected through a brush or brushes or through shaft contacts.

A further feature of the invention consists in such a manner of combination of the calling lines with the contact banks of a line-finder group that the latter can extend a greater number of calling lines than the number of bank contact sets, which exists in the contact bank of a single line-finder. In

this arrangement the line-finders are divided into groups and of the total number of the lines of the group to be extended, a part is connected to the bank contacts of all linefinders of the group: a further part is only connected to the bank contacts of the one group of line-finders and a third part only to the bank contacts of the other group of line-finders. he portion of the lines which is connected to both groups of line-finders is usually extended by the one group of linefinders, but in case all line-finders of this group are engaged, it is extended by a line finder of the second line-finder group.

The line-finders used for the invention may be constructed as rotary switches or rod switches, preferably quick-acting switches are used of the character set forth in the specification of British Patent No. 25%373, which describes the Aldendoril quick-acting switch, whose brushes wipeover their bank contacts at a very high speed.

The invention is represented in the drawing, in which Fig. 1 shows a line-finder group with a position of readiness and nine waiting posi tions. The line-finder can be arranged for any desired number of calling lines, for example, 100. The waiting positions are arranged at the end of the contact bank.

Fig. 2 shows agrou'p of line-finders whose waiting positions are distributed over different subgroups of bank contacts.

Fig. 2? shows 'a modified constructional form of Fig. 2. p

Fig. 3 shows an arrangement in which the number of calling lines to be extended is greater than the number of line connections of a single line-finder. V 1 Fig. 4 shows the circuit of the feeling reay. p

In Fig. 1 S indicates a talking station which is connected by lines lOO, 401 to bank contact sets ['0 of line-finders A A A Let it be assumed that the line-finder contact banks have each 100 sets of bank contacts 74', to of which only a few, for example, 7& 10,, In, etc. and 70 are indicated. To simplify the representation the brushes of all the line-finders from A, to A are-shown as if they all had set themselves on the contact bank of a single line-finder. Actually the brushes each stand on their own contact bank or when an Er'ic sson wire contact bank is used, for example, on diii'erent parts of the contact'bank. Switchesof this general type having wire contact banks are disclosed in British Patent 283,153, accepted "October 18, 1928,.and in British Patent 299,351, accepted OctoberQQ'3, I928. The last nine contact sets 1692 to 70 are arranged as waiting positions w, to Q09 on which the brushes of the line-finder set themselves immediately, as soon as they become free after finishing a talking connection. Each line-finder sets itself on a diiferent waiting position w to 10 If, for example, the moving or setting magnet of a line-finder, for example, M of A is excited in the manner to be explained later by means of a current sent through the brush 6, and contact 18, the contact 17 closes before the contact 18 opens, and the right winding of the setting magnet M then receives current from all contacts 26, 26a, 26?), etc, which are engaged through 14:, 24, 17 until the brush b reaches a dead contact, for example 26h. Then the moving magnet M becomes deenergized and applies, by its contact 16 as well "as-the contacts 24, 14 themselves, the negative pole to the bank contact 2671,, so that no other started line-finder can remain in contact with it. The bank contact strip 26 extends over 91 sets of contacts is, to 70 so that when a line-finder, such as A1, has stopped on it, no other started line finder can stop on a contact set k to 70 if its starting relay R, is not excited, in order to disconnect its brush 6., at 2st from the excited magnet M Such an excitation of the starting relay R always takes place when the started line-finder is to set itself on to a calling line, but otherwise not. In Fig. 1 a line-finder A is located at the beginning of the contact bank. This position of a linefinder is to be indicated as the position of readiness, that is to say, as the position in which it is ready immediately to set itself on any calling line. In each of the waiting positions 10 to w there is a line-finder A to A Thefcircuit arrangement "described in detail presently is so arranged that as soon as the line-finder A, which is in readiness moves on to effect a connection from the position of readiness, the line-finder A, which is in the waiting position/w moves up into the position of readiness in place of A, and at the same time a further line finder A, moves up into the waiting position w Line-finders becoming free from connections move up always immediately to the waiting positions or to the waiting contacts e0 to 10 every such line-finder setting itself on to a different waiting contact. If different linefinders are taken into use by talking connections and if no line-finder is on the last waiting contact w but one of them is on the waiting contact we, the latter is 'caused by an impulse arising from the last'call to move up to the waiting contact w, and then when a further call takes place it springs into the position of readiness and immediately from there moves up to the calling line. So long also as only a single line-finder in "the group is free, it extends every calling line in a fraction of a second (at the mostone-third of a second) to the next switch (group selector or connector). I

A new arrangement, of which the invention makes use, is that of the feeling re lays, which will now be described with the aid of Fig. 4. In this figure 500 and 600 are brushes which connect the magnet windings Ma, Md, with the bank contacts 601, 604. fa to fd are the feeling relays, which are connected to the bank contact 601 to 604. m to ml are release or extending relays. 606 is a resistance located in the moving up starting line. The feeling relays have locking windings, which they "can insert through their contacts 607 to 610. The top windings of the feeling relays fa to fcZ and the magnet windings Ma, Ma? have a resistance which is so small in relation to the windings m to wt that when a relay fa to fol is excited through a resistance 605, '611, 612, 613, the relay m to rd is almost short-circuited and does not attract its armature. Let it now be assumed that the moving up starting line 605 is connected with the negative pole. A current then flows through the resistance 606, top winding of fa, 601, 500, magnet Ma to the positive pole. The feeling relay reacts to this current, inserts its locking winding and disconnects the relay m at the contact 61%. If no magnet Ma is connected with the contact 601 then the feeling relay fa would re main deenergized and the relay m would he energized and apply negative pole to the feeling relay fb. If no magnet fil is connected with the contact 602, the feeling relay fb also remains unexcited and therefore the relay r?) is excited, which now applies the negative pole to the feeling relay fl). Since no magnet is connected with contact 603, f also remains deenergized whilst rc is excited and connects the negative pole to the feel ing relay Since a magnet winding NJ is connected with the contact 604, the feeling relay fd is excited and disconnects the relay rd. It can be seen from this that always either the feeling relay f or the correspond ing extending relay r is excited, according as a small resistance M is connected with the particular felt contact 601 to 60% or not.

The manner of working of the arran ement represented in Fig. 1 may now be describer as a whole: if a subscriber S calls, his line-relay LR is excited by a current which flows from the positive pole throu the left winding of LB, 1, S, 2, right win d ing of LR to the negative pole. The relay LR by opening contact 3 renders the calling line engaged, the contact 5 marks the line in the line-finder contact banks as calling, at contact 4 prepares a circuit through cut-off relay 6 and at contact 6 closes a starting circuit which extends from the negative pole through 6, starting wire 8w, contact S of the relay (51, which bridges over the delay resistance cZrs, lower winding of the feeling relay 83, starting contact 81, contacts 9, 10, starting relay R1 to the positive pole. The feeling relay 83 cuts out the relay 81 at contact 84: and at contact 8% closes a locking circuit for itself whilst the starting relay R1 closes at contact 11 a lockingcircuit for itself extending through the contact 12 before it opens its contact 10. Further at the contact 15 it inserts the setting magnet M1 in a circuit which extends through the brushes b3 and contacts like 5 and prepares at contact an exciting circuit for the setting magnet M1, which is later, at the end of the speaking connection, closed by deenergization of the extending relay al (which at present is not yet excited) through contacts 12, 20, contact 21 (which is now open). The starting relay R1 further opens the contact 2a in order to prevent the negative pole getting into connection through contacts like 5, brush 723, contacts 15, 17, 24, 14:, brush 62 with the bank contact strips 26 since, as appears from the following, by this means the next line-finder A2, which on the starting of the line-finder A1 is moved further out of its waiting position to the contact 26, would obtain an undesired current through its brushes Z22 and its settin magnet M2 which would prevent the stopping of the line-finder A2 at the beginning of its contact bank. The relay B1 also opens the marking contact ml in order to mark th line-finder A1 in the contact banks of the line-finders of the next preselooting stage as calling and at contact 301 closes the relay R1 of a starting circuit for a line-finder of the next preselecting stage. Finally the relay R1 inserts at contact hl first the relay (Zr, which inserts the delay resistance (ZTS in the starting circuit 810 and secondly a starting circuit from the first linefinder A2 located in the waiting position. This starting circuit causes the advance of the line-finder A2 to the contact strip 26 of its contact bank and extends from the negative pole through 7L1, advance starting line 27, resistance 11, reeling relay f1, contact 28 of the second feeling relay f2, the waiting contact wl of the contact bank of the line-finder A2, contact 18 of the setting magnet M2, which now connects itself through its contact 17 with its brush b2 and liberates its set of brushes so that the same aovances up to its bank contact strip 26 which on account of the opening of the contact 24 of the line-finder A1 set on the calling line is insulated. The setting magnet M2 loses its excitation therefore when the brushes of the line-finder A2 reach its bank contact strip 26 and this line-finder consequently remains stationary at the beginning of its contact bank and closes its starting contact 82. An excitation of its starting relay R2 through the starting line Sil by the call which has started the linefinder A1 is prevented by the delay resistance (Zrs which is not bridged over until the line-finder A1 reaches the calling subscribers line and its extending relay G1 has responded and its starting relay R1 is caused by opening of the maintaining current contact 12 to allow all its contacts to go back into their normal positions (up to contact 20, which is still kept closed by a slight excitation through the left winding of R1, resistance and contact 13), the bridging over relay (Zr being disconnected at contact 721 and the delay resistance being bridged over. Since the starting line sw simultaneously with the response of the extending relay 01 on account of the excitation of the cut-off relay 6 (+6, 4, b4, 01, and the deenergization of the line relay LR at contact 6 is disconnected from the negative pole, if a further line has not called in the meantime,

no excitation of the starting relay R2 through the now closed starting contact 82 of, the line-finder A2 takes place and this line-finder now waits at the beginning of its contact bank for the next call.

As the line-finder A2 was started through the feeling relay fl and its waiting contact wl the feeling relay fl was excited by its upper winding and closed at contact 51 a maintaining circuit extending through the lower winding of the feeling relay, the resistance W1 and contact k1, which circuit was interrupted as soon as the line-finder Al had reached the calling line and thereby its starting relay R1 opened its contact 7L1. If at the opening of the contact h]. of the first line-finder A1 already a second call had come in or shortly thereafter a second call comes in then the starting relay R2 of the second line-finder A2 located in the relay position is excited in the manner described for the starting relay R1 of the first line finder A1 and the second line-finder A2 sets itself on the calling line, for example, line No. 99, whereby its contact 712 remains closed until it has found this line and extended it to the next selecting stage. Whilst the linefinder A2 is hunting for the calling line No. '99 -'a current flows through the contact 7L2, the lnlOVl l lg up starting line, resistance 11-, back contact 52 of the feeling relay fl (which new cannot be excited through its top winding because no line-findcr stands on the waiting contact 101), top winding of the release relay re to the positive pole. The release relay re closes at the contact 33 a maintaining circuit for itself extending through the contact and its lower winding and by means of contact 32 applies, the negative poleto the second feeling relay f2. If nowca third line-finder A3 is located on the waiting contact 102 of its contact bank, then the feeling relay f2 is excited by means of its top winding and at the same time the starting relay of the third line-finder A3 which is connected similarly to the other starting relays R1, R2 receives a starting current so that the third line-finder moves up to the waiting contact wl. As soon as tne third line-finder A3 leaves the waiting contact L02 the current flowing second feeling relay f2 and the waiting contact Q02 is interrupted. At the contact 28 ofthe falling feeling relay a new starting circuit for the third line-finder A3 is closed, extending through the feeling relay fl, contact k2 of the second line-finder A2 and the'wa'iting contact wl, this circuit causing the third line-finder A3 to go into the ready position, that is to say, to set itself at the beginning of its cont-act bank.

At the moment when the feeling relay fl is excited by this starting current it opens at contact 52 the current path from the advance starting line 27 to the upper winding through the of a release relay re and at the same time it opens at contact the'maintaining circuit of the release relay re extending through contact 30 of the feeling relay 72 so that the release relay is deenergized. Before this deenergization of the release relay r@,'however, at the falling off of the feeling relay f2, which closes its contact 54 earlier than the contact 28, caused by the movement away of the line-finder A3 from the waiting contact Q02, the group starting relay ga has been excited by a current extending from the negative pole, through 32, 7'2, 54, ga to the positive pole. The group starting relay ga lets its armature fall off gradually, so that it closes at contact 31 the group starting circuits which extend from the negative pole through 29, 70, contact 80 of the extending relays of all line-finders not actually engaged by calls or effected connection, contact 19 of the setting magnets, of these line-finders their second windings to the positive pole. By this means these line-finders all obtain a starting impulse which causes them more one or several Waiting contacts further. The group starting line at the contact 31, only remains excited in the time which elapses between the excitation of .900 (negative pole, 32, T2, 54, ga, positive pole) caused by the movement away of the linefinder A3 from the waiting contact 102 and the deenergization of the release relay re which on its part is effected by the excitationof the feeling relay f1, when the line- 'iinder A3 reaches the waiting contact @0 1,

and the contact 28 is closed. The closing of the contact 28 is effected by the deenergization of the feeling relay f2, which takes place on the movement away of the l ine finder A3 from the Waiting contact e02 simultaneously with the excitation of the group starting relay ya, just mentioned. If new a fourth line-finder A l reaches the waitcontact r02 before the release relay falls off through the opening of its maintaining circuit taking place at contact 60, the impulse relay of the fourth line finder Adreceives a current flowing from the negative pole through 32, 1'2, feeling relay f2, waiting contact 102. The feeling relay opens at its contact 29 the group starting circuit, so'that all line-finders started in group vmanner are stopped and only the fourth line-finder moves further from the second waiting contact 102 to the first waiting contact wl. From this contact the third line-finder A3 has already moved off and gone over into the ready position,

For the next (third) call everything is now prepared, that is to say, a line-finder A3 is located in the ready position and a further line-finder is on the waiting contact Q01.

if no fourth-line finder A4 should have the moment of the opening of the 'grmip starting circuit at contact 31, then for the next (third) call the line-finder A3 is located in the-ready position, but no further line-finders have set themselves on the waiting contacts e01, 102. In such a case on the next call the line-finder located in the ready position is started in the above described normal manner by its starting relay It and at the same time the release relay re is excited through the advance starting line 27, resistance W1 and contact 52. The release relay inserts the group starting relay a through 32, T2, 54 and the latter closes at its contact 31 the group starting circuit (negative pole, 29, 31, '10, contact 80 and 19 of all disengaged line-finders, left magnet windings of the setting magnets of all these line-finders). These line-finders then all move further in their contact banks until one of them reaches the waiting contact 102 and thus excites the feeling relay f2, and the group starting circuit is opened at contact 29. The line-finder which has reached the waiting contact 102 is then, as already described above, caused to first advance to the waiting contact wl and then Passover into this ready position. It will certainly only do the latter when the moving up starting circuit 27 is closed at a contact 72., that is to say, when the calling line which has caused this advance to the waiting contact 101, has not yet been extended by the line-finder A4 which has last been in the ready position up to the next selecting stage. If the moving up starting circuit is already opened then the next line-finder advancing to the ready position remains stationary on the waiting contact 101, its starting contact 8, therefore, remains open so that at first itcannot be brought in the usual manner into motion by its armature relay R. In such a case it receives through the group starting circuit 70 an impulse owing to the fact that the relay 81 which ordinarily does not become excited, because the current is withdrawn from it by the winding 83 and right winding of a starting relay It which have low ohmic resistance. The relay 81 is in this case excited by a current flowing through the starting line S10, contact 8, resistance 13, contact 84: and connects by means of its contact 82 the negative pole to the group starting line 70. The line-finder resting on the waiting contact e01 is thus started to go into its ready position. The right-winding of its starting relay now receives a current flowing also through the lower winding of the relay 83. The starting relay R of the line-finder is excited and the line-finder proceeds further to the calling line, whilst the relay 81 at contact 84 is immediately cut out and thus the group starting circuit is again opened after it has caused the disengaged line-finders to move further one or perhaps several Waiting contacts. In any case the line-finders started in this manner again set themselves each on a waiting contact diflerent from the remaining waiting contacts.

Instead of providing the waiting positions of the line-finders all at the end of their contact banks, as in Fig. 2, the arrangement can be made such that the line-finders which are not in use distribute themselves with reference to one another uniformly over the whole contact banks so that, for example, one line-finder is started in front of the bank-contact group of the first ten connected lines, a second in front of the bank contact group of the second ten lines, and so on, by a call from the group of ten lines in question and only receives impulses by calls from another group or groups when in such a group at the moment of a call in the same, no line-finder stands in readiness. Such an arrangement is shown in Fig. 2. In this figure, 910, 920 gOO indicate the first, second and tenth subgroup each of ten bank contact sets of the line-finder for 100'lines altogether. The third to the ninth sub-group are omitted in the figure. The brushes of five line-finders Aa, Al), A0, A2, A3 are distributed on the contact bank. In reality the brushes of each line-finder have, of course, a contact bank for themselves, if wire contact banks or panal selector banks are not employed. The line-finders are all arranged like those of Fig. 1 with the exception that they each have a special current leading brush for their starting relay R. The linefinder Aa has a special brush aa, the linefinder A7), a special brush ab and so on. These special brushes wipe over long bank contacts 2a, 2?), etc. The strips ea, 2?), etc. of the first nine sub-groups each extend through the ten bank contact sets of the subgroup. In the tenth sub-group the strip 29 extends, however, only over eight contact bank sets, so that the brushes a2, a3 of the two line-finders which have set themselves in the last two positions or onthe waiting contacts e01, e02, do not stand on current leading strips. If no talking connection is made, then a line-finder Aa, Ab, etc. stands at the beginning of each subgroup of bank contact sets and a line-finder A2, A3, each stands on the waiting contacts e01, 102 so that a total of twelve line-finders exists.

7610 indicates armature contacts of the line-relays of the first sub-group of ten lines, 7020 armature contacts of the line-relays of the second sub-group of ten lines and 7400 armature contacts of the tenth subgroup. To each sub-group corresponds a starting selecting relay g1, g2, 90 which connects the starting line s-w through the lower winding of the relay 83 with the current leading strips ea, 2?), or 20 of the calling subgroup. If a subscriber of the second sub-group calls, then the relay 92 is excited the excitation bein effected through a line-relay contact 01" the calling sub-group, for example, contact 101, and

at the same time the negative pole is applied through the associated line contact relay 100 through the contact of the relay (51' (which corresponds to the relay of Fig. 1 indicated in the same manner) and through the starting line s'w to the feeling relay 83, which is now excited by the current flowing through contact 95, 25, ab, 9, 10 and the starting relay Rb and disconnects the relay 81. The line-finder A 0, which stands at the beginning of the group 20 of bank contact sets which corresponds to the call ing sub-group, now sets itself on the calling line of this sub-group. At the same time in the manner described in connection with the explanation of Fig. 1, by means of a current flowing through the moving up starting line as well as through the resistance T1 and. the feeling relay f1, the linefinder standing on the waiting contact Q01 is started and caused to move in place of the line-finder Ab towards the beginning of group. 920 or towards the one group 910, lying in front if another line-under has not already set itself thereon.

f The brushes cm, at etc., ea, 6?) etc., as well as the bank contacts 20,, 25, etc., ea, (Z?) etc. and r01, r02 operated by these brushes may be replaced by shaft contacts, so that the line-finders only haveiour' brushes and the tour bank contact rows belonging thereto. For example, the line-finder Aa may be provided in place of the brush ac and the banlr contacts 2a, 26 etc., wiped over by it, with a shaft contact which is closed avlren the brushes of this line-finder stand tie be ginning of the first bank contact sub-group glO, whilst the shaft contact replacing the brush at of the line-finder A?) and the contact wiped over by it closes, when the brushes of this line-finder stand at the beginning of the sub-group 920 and the shaft contact of the line-finder A replacing the brush ac closes when its brushes set themselves on the third sub-group1 Furthermore, the relays g1, g2, may be dispensed with when the line 100 or the relay 83 is connected directly by the group selecting contact 101 of the line relay with the bank contacts ea, so etc. instead of by the relays g1, g2 etc., as is indicated in Fig. 2a.

In the previously described arrangements, the number of lines to be extended by a group of line-finders, is at the most, equal to the number of brush positions or bank contact sets of a line-finder. In other words, it is possible to extend by means of a hundred gpoint line-finder, for xainp1e ,,at the most one hundred lines. Fig. .3 an arrangement is shown which makes it possible extend more lines than there are contact sets or brush positions in the contact bank of a line-finder. Tit, for example,

150 lines are to'be extended instead of 100 lines according to the new arrangement, 100 lines are connected to the bank contact sets of a group of lOO-point line-finders and the 50 further lines to the bank contacts of a iurtner group oi line-finders. It the line-finders of the second group are also 100- point switches then contact sets remain free in their contact banks for a further 50 lines. To these contact sets may now be connected 50 lines of the first mentioned 100 lines which are already connected to the first group of line-finders so that a group of 50 lines arises which can be extended both through the first as well as through the second group of line-finders and can be used for the extension of any desired kinds of lines, for example, subscribers lines or trunks. In Fig. 3, this arrangement for the extension of line-finders of a first preseleeting stage, is represented.

A81, A520, A521, are three line-finders of the second preselecting stage of which Asl, A520, are to represent a group of 1 00-point line-finders and A821 a second group of 100'- point line-finders. To the first 50 bank con tact sets 50a of the first group of line-finders A81, A820, of which only five are shown, is connected 2. group of 50 trunks coming from the first line-finders. These trunks are dis tinguished by their associated relays R1 and contacts ml, which correspond to the relays E and contacts m of Figs. 1 and 2. To the second 50 bank contact sets 00a of the first line-finder group A81, A520, of which also only five are shown, is connected a second group of 50 trunks coming from the first line-finders. These are distinguished by their associated relays R11 and contacts m2. This second group of trunks is also connected to the first 50 bank contact sets 00a of the second line-finder group A321. This first line-finder group A81, A320 can extend therefore all the lines of the first and second group of 50 trunks each (R1 and R11), whilst the second line-finder group A321 can extend both the second group of lines 00a but not the first 50a. To the second group 150a of 50 bank contact sets of the second line-finder group A821, is connected a third group of 50 trunks which are distinguished by the relays and their associated contacts m3 (which correspond to the relays R and contacts m of Figs. 1 and 2) This third group 150a; of trunks can be extenced only by the line-finder group A821. I

The total number of 150 lines formed by the three groups of 50 trunks each, is divided into ten groupseach of 15 lines which each serve a subscriber group of 100 lines.

Two such groups of trunks each serving 100 subscribers lines are indicated in Fig. S'by' GI and-G11. Two sub-groups RI, RILeach of five, lead from'each ofthese groups to the contact banks of the first line-finder group A81, A820, and one of these sub-groups, namely RII, leads to the contact banks of the second line-finder group A821. The third sub-group RIII of each group GI, GII etc. is led towards the contact banks of the second line-finder group A821.

The 100 subscribers lines which are served by a group of trunks, for example, GI, can, therefore, be extended either through the first line-finder group A81, A820 or the second line-finder group A821.

If the trunk of the first two sub-groups R1, R11 is taken by a call, by means of the starting wire 810a, a line-finder of the first group A81, A820 started in the manner described in connection with the explanation of Figs. 1 and 2. If all the line-finders of the group A81, A820 are engaged and it the calling trunk belongs to the second subgroup RII, a line-finder of the second group A821 is then started. If a trunk of the third sub-group RIII is taken by a call in any one group GI, GIT, by means of the starting wire 8100, there is started a line-finder of the second group A820 of line-finders.

The line-finder group A81, A820 is provided with relays 83a, 81a and the linefinder group A821 with relays 83b, 82?) which correspond to the relays 83, 82 oi Fig. 1, so that a description of their circuits and manner of operation is not necessary here. t is only necessary to take into account the case when a trunk the sub-group RH in any one group GI, GIT is to be extended when all line-finders of the first linefinder group A81, A820, are engaged. Then the line 200 is disconnected from all relays R and by means of open contacts 84; or 9, which correspond to the contacts 8 and 9 of Fig. 1, and relay 83 remains on the closure of a contact m2 deenergized, whilst the relay 81a is excited (from negative pole, a contact m2, 810a, d'rs, 1, 84a, 81, positive pole) and at its contact 82a inserts an exciting current for the relay 201 extending through the contact 209 of the feeling relay 202. The feeling relay 202 remains deenergized because the line 210 is disconnected at all contacts 80 from the second windings of the magnets M. The relay 201 applies the negative pole to the contact 221 of the relay 230, and this is excited by a current which flows through the auxiliary starting line asw, which is connected to the negative pole by means of the relay BIT of the particular calling trunk through its contact, for example, 300. There flows therefore through the contacts 220, 221, a current through the resistance 1%, relay 837), a starting contact 86 of a line-finder A821 and its starting relay R, whereby the particular line-finder A821 is started to set itself on the calling trunk.

The line-finders A81, A820, A821 may also be arranged like those shown in Fig. 2 so that their brushes are distributed in a ready condition on different contact groups of the contact banks.

In order to supervise the amount of trafiic by means of the relay 201, a signal can be inserted which always appears when all the selectors of the first group A81, A820 are engaged. A similar signal can be provided by the relay 81b in the group A821.

I claim 1. In a telephone exchange system a plurality of calling lines, a plurality of line finders for extending said lines, and means for causing each line finder to move to a waiting position and then to a position of readiness prior to executing its line finding movement.

2. In a telephone exchange system a plurality of calling lines, a plurality of line finders'for extending said lines, and means for causing each line finder to move from a waiting position and thento a position of readiness prior to executing its line finding movement, each of said line finders having a different waiting position.

in a telephone exchange system, a plurality of sets of line finder brushes, a waitpesition and a position of readiness for each set of brushes, and means for moving brush from a Waiting position to a ion of readiness prior to said brush set using uset to hunt for a calling line.

A. In a telephone exchange system, a plurality of sets of line finder brushes, a waiting position and a position of readiness for each brush, means effective when one set of brushes moves from its position of readiness to find a calling line for causing another set to move from waiting position to a position of readiness.

5. in a telephone exchange system, the m thod of operating line finders which comprises moving a free line finder to hunt for a callin line, moving another one of the free line finders from a waiting position into a position of readiness, and moving all the remaining tree line finders into waiting positions.

6. In a telephone exchange system, a plurality of line finders, means responsive to the initiation of a call for moving a free one of said line finders to hunt for the calling line and for automatically causing another one of the tree line finders to move from a waiting position to a position of readiness and for causin all remaining tree line finders to move into waiting position.

7. In a telephone exchange system telephone lines, a plurality of line finders, a contact bank in which said lines terminate certain or" said contacts serving as waiting positions for said line finders, and other of said contacts serving as positions of readiness for said line finders, means for advancing each line finder from awaiting position to a position of readiness to extend calls, and a finder allotter mechanism controlled by the movements from waiting to ready positions of the. line finders.

8. In a telephone exchange system, a plurality of line finders of the non-restoring type each adapted to be moved to a waiting position and to a position of readiness prior to executing its line finding movement,

means effec ive when no free finders are in a waiting position and responsive to the initiation of a call for causing all the free finders to move to a waiting position and for causing one of said free finders to go to a position of readiness and then on to the calllng line.

9. In a telephone exchange system, a pluv rality of line finders of the non-restoring type each adapted to be moved to a waiting position and to a position of readiness prior to executing its line finding movement, each of. said finders having a different waiting position, means effective when no iree finders are in a waiting position and responsive to the initiation of a call for causing all the free finders to move to a waiting position and for causing one of said free finders to move to a position of readiness and then on to the calling line.

10. In a telephone exchange system, a

bank of contact sets a pluralit of brush ment, means comprising a plurality of feeling relays for feeling certain of said bank contacts to ascertain whether any of said brush sets are in contact therewith in waiting position, and means effective when such a waiting brush set is revealed for advancingthe same to a position of readiness.

1.2. In a telephone exchange system, a con tact bank, a plurality of line finder brushes,

each brush having a different waiting position before said contact bank, a feeling relay associated with each waitingposition, means responsive to the initiation of a call and including said feeling relays for causing a line finder in waiting position to move to a position of readiness, a group starting relay, and means effective when none of said line finders is in waiting position for causing said group start relay to move all remaining free line finders toward a waiting position.

13,. In a telephone exchange system, a contact bank, a plurality of line finder brushes, each br vsh having a different waiting position before said contact bank, a feeling relay associated with each waiting position, means responsive to the initiation of a call and including said feeling relays for causing a line finder in waiting position to move to av position of readiness, a group starting relay, means effective when one of said line finders is in waiting position for causing said group start relay to move all remaining free line finders toward a waiting position, and means effective when said free line finders have reached their waiting positions forcausing one of said finders to move to aposition of readiness and then on to the calling line.

14. In a telephone exchange system, a contact bank, the contacts being arranged in sub groups,'a plurality of line finder brush sets each set having a waiting position before a different sub-group, of contacts, a feeling relay associated with each waiting Positio means responsive to the initiation of a, call and including said feeling relays for causing a line finder in. waiting position to move to a position of readiness, a group starting relay, means effective when none of said line finders is in waiting position for causing said group start relay to move all remaining free line finders toward a waiting position, and means effective when said free line finders have reached their waiting positions, for causing one of said finders to move to'a position of readiness and then on to the calling line.

15. In a telephone system a bank of con-' tacts, a plurality of line finders each having a different waiting position before said bank contacts and positions of readiness before other bank contacts, a common start wire, means responsive to the initiation of a call for marking said wire to start a line finder which is in a position of readiness, and a common advance wire adapted to be marked under control of said start wire to control the movement of the free line finders from waiting positions to positions of readiness in sequence.

16., In a telephone exchange system a con tact bank, groups of line finders, a starting relay for each group, a starting circuit including a line finder brush and one of said bank contacts, said starting circuit including a different bank contact for each line finder. 17 A telephone system according to. claim 16 characterized in this that the said start circuits include contacts controlled by the line finder brush shafts.

In testimony whereof I have affixed my signature.

FRITZ ALDEND ORFF. 

